Thermal barrier systems for panel installations for store front framing systems and the like are well-known. Typically, such a framing system includes inner and outer metal frame elements connected by a thermally insulating coupler member, with channels being formed on the frame elements to receive the edges of infill panels.
Numerous methods are known for securing the thermally non-conductive connector to the inner and outer frame elements. In one type of connection known as a "twist-in" connection, the connector has a base which is rotatable into lockable engagement with a locking channel defined in one of the frame elements. In a second type of connection known as a "snap-in" connection, the connector has a pair of resilient legs which snap outwardly to bring flanges formed on their outer edges into locking engagement with a pair of opposing slots defined on one of the metal elements. With a third type of connection known as a "snap-on" connection, a pair of resilient legs having flanges formed on mutually facing portions receive a locking flange therebetween and snap inwardly into grooves formed on the lateral edges of the locking flange.
An example of a prior art thermal barrier system for store front framing installations and the like is found in U.S. Pat. No. 4,117,640. Inner and outer metal elements receive the edges of infill panels therebetween and are connected by a thermally non-conductive coupler member. The coupler member has a twist-on connector formed at its base which is rotatable into locking engagement with a pair of slots defined on the inner metal element. The coupler member further has a snap-in connector formed at its opposite end which snaps into locking engagement with a pair of slots defined on the mutually facing portion of the outer metal element.
Thermal barrier systems such as that disclosed in the aforementioned U.S. Pat. No. 4,117,640 suffer a number of disadvantages. First, the legs of the coupler member which are twist-lockable into engagement with the locking channel are dependent upon a snug fit and the resiliency of the coupler material to remain locked in place. Such a design does not afford accommodation for manufacturing tolerances in either the locking channel or the coupler member. Further, exposure to the elements over a period of time may cause the coupler member to lose some of its resiliency. Accordingly, extrusion tolerances or a loss of resiliency can permit the coupler member to slide within the locking channel.
The sliding of the coupler member within the locking channel can have a number of adverse consequences. First, if the twist-in clip cannot be fixed securely in place, it will be impossible to preinstall the clips, and the clips will have to be installed in the locking channel at the job site. The inability to preinstall the clips will increase the labor costs incurred in installing the clips, since clips installed by skilled labor at the job site will incur a higher labor rate than would be incurred by shop labor or by an automated or semi-automated installation procedure which would be possible only in the shop. Further, a worker installing clips in the friendly environment of a warm shop will be able to install the clips faster and more accurately than a worker battling inclement weather at the job site, possibly wearing gloves to protect against the elements.
Thus, there is a need to provide an insulating glazing clip which can be preinstalled onto one of the frame members prior to delivery to the job site.
Furthermore, clips which are not securely anchored within the locking channel can still slide within the channel even after installation. Wind loads on the storefront panels and temperature fluctuations whereby the outside frame member thermally expands and contracts more drastically than the interior frame member can create forces on the clip which would tend to displace it if it is not securely anchored. Particularly in vertical frame members, the clips can slide toward the lower end of the locking channel, permitting the upper end of the frame member to separate.
Accordingly, there is a need to provide a twist-in coupler member which can be securely anchored within its locking channel.
A further disadvantage of the storefront framing system disclosed in the aforementioned U.S. Pat. No. 4,117,640 is the inability of a single clip to accommodate glazing panels of different thicknesses. For example, if it is desired to increase the spaced-apart relation between the frame members to accommodate a one inch thick glazing panel, rather than a one-quarter inch panel, it is necessary to provide a coupler member which is three-quarters of an inch longer. Not only is it an added effort and expense to maintain an inventory of a variety of different lengths of clips, but also the potential is introduced for accidentally installing the wrong clip for a particular application.
Accordingly, there is a need to provide a storefront framing system wherein a single clip can accommodate infill panels of different thicknesses.